Printing medium feeder and image forming apparatus having the same

ABSTRACT

A printing medium feeder and image forming apparatus are provided. The printing medium feeder includes a pickup unit configured to pick up printing medium, and a support arranged on a lower side of the pickup unit to selectively support the pickup unit or release supporting of the pickup unit, wherein as the support releases the supporting of the pickup unit, the other end portion of the pickup unit descends by self-weight on the basis of one end portion thereof to be seated on the printing medium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to, and claims priority benefit, under 35 U.S.C. §119(a) to Korean Patent Application No. 10-2014-0104431, filed on Aug. 12, 2014, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field

The present disclosure relates to a printing medium feeder and an image forming apparatus having the same, and more particularly to a swing type paper feeder that can reduce noise during paper feeding.

2. Description of the Related Art

To perform printing operation through an image forming apparatus, paper may be transported to a feed cassette or paper may be set in a feed tray to an inside of the apparatus, and a paper feed type may be classified as an up-down type or a swing type.

An up-down type feeder includes a pickup unit that may be fixed to an upper side of a feed cassette to transport paper sheet by sheet. Accordingly, when the feed cassette including paper is mounted on the image forming apparatus, a knock-up plate that may provided on the feed cassette ascends to move the paper in a direction of an upper side on which a pickup unit exists. One end of the knock-up plate may be hinge-engaged and the other end thereof may be connected to a driving portion that may include a motor and gears. In accordance with driving of the driving portion, one side surface of the knock-up plate ascends, and thus a part of the paper can reach the pickup unit. The up-down type feeder may be used in a large-scale image forming apparatus, and a large amount of paper, for example, about 500 sheets of paper can be loaded on the paper cassette at a time.

A swing type feeder includes a pickup unit that swings upward and downward to transport paper sheet by sheet. Accordingly, when a feeding operation starts after the feed cassette in which paper fills is mounted on the image forming apparatus or paper is set in a feed tray, the pickup unit may be rotated in a paper direction to reach the paper. The swing type feeder may be used in a small-scale image forming apparatus, and, for example, about 50 to 100 sheets of paper can be loaded on the paper cassette at a time.

According to the swing type feeder, the pickup unit may be spaced apart from the paper without coming in contact with the paper before the printing operation, but when the printing operation starts, the pickup unit may be rotated to make a pickup roller provided on the pickup unit reach the paper. When the pickup roller reaches the paper, the paper may be transported to the inside of the image forming apparatus by a rotating force that may be transferred from a driving source. Thereafter, if one sheet of paper is transported, the driving source stops its operation, and thus the pickup roller also stops rotation to print the paper sheet by sheet. A restoring force of a return spring of a housing member returns the pickup unit to a standby state. That is, after one sheet of paper is transported, the pickup unit again becomes spaced apart from the paper. Thereafter, if the driving source re-operates to transport the next paper, the pickup unit is rotated in the paper direction, and thus the pickup roller reaches the paper.

However, according to the swing type feeder in the related art, whenever one sheet of paper is transported to the inside of the image forming apparatus, the pickup roller may collide with the paper due to the rotation of the pickup unit, and impact noise is generated. The impact noise may be loud, and unpleasant to a user.

The impact noise may not be generated in the up-down type feeder that does not perform the swing operation. However, the up-down type feeder is relatively expensive in comparison to the swing type feeder, and it may be difficult to adopt the up-down type feeder in a typical small-scale image forming apparatus. Accordingly, an inexpensive swing type feeder is used in a small-scale image forming apparatus regardless of the noise.

The noise generated may become greater as the speed of the swing operation becomes higher and the section of the swing operation becomes longer. However, since reduction of the swing operation speed may be related to the printing speed, lowering of the paper transport speed of the pickup unit may not meet high-speed printing requirements. Further, since reduction of the swing operation section may be related to the amount of paper load, it may be required to reduce the amount of paper load to reduce the noise, or it may be required to use the up-down type in which the height of the feed cassette is varied according to the amount of paper. However, the up-down type in which the height of the feed cassette is varied may require the separate feed cassette, which may be mounted on the image forming apparatus so that the height of paper can be heightened by a spring and the driving force, and this it may be difficult to adopt the up-down type in the image forming apparatus in which only the feed tray exists without the feed cassette.

SUMMARY

Additional aspects and/or advantages will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention.

According to an exemplary embodiment of the present invention, the above problems and/or disadvantages are addressed and the exemplary advantages described below are provided. Accordingly, an aspect of the present disclosure a paper feeder is provided that can reduce noise that is generated whenever a pickup unit repeatedly reaches every sheet of paper to transport the paper.

According to an aspect of the present disclosure, a printing medium feeder includes a pickup unit configured to pick up printing medium, and a support arranged on a lower side of the pickup unit to selectively support the pickup unit or release supporting of the pickup unit, wherein as the support releases the supporting of the pickup unit, an other end portion of the pickup unit descends by self-weight on the basis of one end portion thereof to be seated on the printing medium.

The support may swing about a lower end portion thereof to support a part of a lower side of the pickup unit through an upper end portion thereof.

The support may be pressed by a feed cassette mounted on a main body or the printing medium set on a feed tray and may swing in a mounting direction of the feed cassette or in a printing medium setting direction to release the supporting of the pickup unit.

The support may include an elastic member provided in the lower end portion thereof, and may return to its original position by the elastic member to support the pickup unit if the feed cassette secedes from its mounted position or the printing medium set on the feed tray is entirely consumed.

The support may include a support roller provided on the upper end portion thereof to come in contact with and to slide along the part of the lower side of the pickup unit.

The pickup unit may include a guide projection formed to project from the lower side thereof in a side direction, and the support may include a support roller configured to support the guide projection.

The pickup unit may include a pressing member configured to elastically press the other end portion of the pickup unit so that a pickup roller arranged on the other end portion of the pickup unit presses the printing medium.

The pressing member may be a torsion spring provided on a driving shaft that penetrates the one end portion of the pickup unit.

The pressing member that presses the other end portion of the pickup unit in a lower direction may be a coil spring that presses from an upper portion of the pickup unit toward the lower side.

The coil spring may have one end that is fixed to a part of a structure that is positioned on an upper side of the pickup unit and the other end that is fixed to an upper side of the other end portion of the pickup unit and may elastically press the pickup unit.

According to an aspect of the present disclosure, a printing medium feeder includes a pickup unit configured to pick up printing medium; and a support arranged on a lower side of the pickup unit, wherein the support is selectively set to a first position in which the support supports the pickup unit or a second position in which the support is pressed by a feed cassette that is mounted on a main body or the printing medium that is set on a feed tray of an image forming apparatus to release the supporting of the pickup unit.

The pickup unit may be rotated so that the other end portion thereof descends by self-weight on the basis of one end portion thereof to be seated on the printing medium as the support is rotated from the first position to the second position, and may be rotated so that the other end portion thereof ascends on the basis of the one end portion thereof as the support is rotated from the second position to the first position.

The support may include an elastic member provided in a lower end portion thereof to be elastically rotated from the second position to the first position.

According to an aspect of the present disclosure, an image forming apparatus includes a main body, a feed cassette detachably provided on the main body or a feed tray provided on the main body to set printing medium; and a printing medium feeder including a pickup unit configured to pick up the printing medium, and a support arranged on a lower side of the pickup unit to support the pickup unit in a first position and to release the supporting of the pickup unit in a second position, wherein the other end portion of the pickup unit swings downward from the second position by self-weight on the basis of one end portion thereof so that a pickup roller of the pickup unit is seated on the printing medium.

The support may be rotated from the first position to the second position as the support is pressed by the feed cassette mounted on the main body or the printing medium that is set in the feed tray.

The support may be rotated from the second position to the first position as the support is released from being pressed by the feed cassette or the printing medium of the feed tray.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the present disclosure will be more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a paper feeder according to an embodiment of the present disclosure;

FIG. 2 illustrates an exemplary paper feeder;

FIGS. 3 and 4 illustrate exemplary states where a support of a paper feeder according to an exemplary embodiment of the present disclosure is set to a first position and a second position, respectively;

FIG. 5 illustrates an exemplary state where a torsion spring is installed on a paper feeder according to an embodiment of the present disclosure;

FIG. 6 illustrates a coil spring provided on a paper feeder according to an embodiment of the present disclosure;

FIG. 7 illustrates a paper feeder according to an embodiment of the present disclosure;

FIGS. 8 and 9 illustrate exemplary states where a support of a paper feeder according to an embodiment of the present disclosure is set to a first position and a second position, respectively;

FIG. 10 illustrate a paper feeder according to an embodiment of the present disclosure in a state where a support is set to a first position;

FIG. 11 illustrate an exemplary state where a support is set to a second position as paper is set in a feed tray;

FIG. 12 illustrate an exemplary state where paper is fed by a pickup roller;

FIG. 13 illustrate an exemplary paper feeder according to an embodiment of the present disclosure in a state where a support is set to a first position;

FIG. 14 illustrate an exemplary state where a support is set to a second position as paper is set in a feed tray; and

FIG. 15 illustrates an exemplary state where paper is fed by a pickup roller.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.

Paper feeders 1, 1 a, 1 b, and 1 c according to an embodiment of the present disclosure are described in detail with reference to the accompanying drawings. Well-known functions or elements may not described or illustrated in detail if it is determined that such detailed description would obscure the present disclosure in unnecessary detail.

Referring to FIGS. 1 and 2, a paper feeder 1 according to an embodiment of the present disclosure includes a pickup unit 100 and a support 200.

The pickup unit 100 includes a driving shaft 110, a pickup roller 120, a power transfer portion 130, a housing 140, and a feed roller 150.

The driving shaft 110 may have one end that is connected to a driving source, and receives a power from the driving source to be rotated. As the driving shaft 110 is rotated, the pickup unit 100 may be rotated in a direction in which the pickup roller 120 descends about the driving shaft 110 as a rotating shaft. The pickup roller 120 may be rotated to transport paper.

The pickup roller 120 may be rotated to transport the paper, and includes a connection portion 121 and a feeder portion 122.

The connection portion 121 may be connected to the power transfer portion 130, and receives the power of the driving shaft 110 to rotate the pickup roller 120.

The feeder portion 122 is a portion that may come in contact with the paper to transport the paper, and may be rotated to transport the paper according to the rotation of the connection portion 121.

The power transfer portion 130 may be arranged between the driving shaft 110 and the pickup roller 120, and transfers the power of the driving shaft 110 to the pickup roller 120. The power transfer portion 130 may include gears that can be gear-coupled to a part of the driving shaft 110 and a part of the pickup roller 120. Accordingly, the rotating direction of the power transfer portion 130 may reverse to the rotating direction of the driving shaft 110 and the pickup roller 120.

The housing 140 is a cover of the pickup unit 100 on which the driving shaft 110, the pickup roller 120, and the power transfer portion 130 may be mounted.

The driving shaft 110 may be coupled through a pair of first coupling holes 141 formed on both side surfaces of the housing 140. The pickup roller 120 may be coupled through a pair of second coupling holes 142 formed on both side surfaces of the housing.

The driving shaft 110 and the pickup roller 120 that are coupled to the housing 140 may be coupled to slip through the first coupling holes 141 and the second coupling holes 142 of the housing 140, and thus can be rotated separately from the housing 140.

The housing 140 may include a supported portion 143 that is a portion that may be contacted when the support 200 supports the pickup unit 100. According to an exemplary embodiment, a housing 140 may include a guide projection 144 that is formed to project from a side surface on which the support 200 is arranged.

The feed roller 150 secondarily transports the paper that may be primarily transported by the pickup roller 120 to the inside of the image forming apparatus. The feed roller 150 may be inserted into the driving shaft 110, and may be rotated together with the driving shaft 110.

The support 200 includes a first portion 210 that forms an upper portion and a second portion 220 that forms a lower portion.

The first portion 210 is a portion that supports the pickup unit 100, and a rear end of the first portion 210 may be connected to the second portion 220.

The first portion 210 has a first surface 211 that is provided at an upper end thereof. The first surface 211 comes in slidable contact with the supported portion 143 that may be formed on the side surface of the housing 140.

The second portion 220 may be arranged on a lower side of the first portion 210, and includes a rotary shaft 221 that is rotated together with the first portion 210 and a fixed shaft 222 that may be rotatably coupled to the rotary shaft 221.

The first portion 210 may be formed to extend from an outside of the rotary shaft 221, and the rotary shaft 221 may be rotated together when the first portion 210 is rotated. A hollow may be formed in the rotary shaft 221 so that the fixed shaft 222 penetrates the rotary shaft 221.

The fixed shaft 222 may be rotatably coupled to the rotary shaft 221, and operate as a rotating shaft when the first portion 210 and the rotary shaft 221 are rotated. That is, the fixed shaft 222 may not be rotated even if the first portion 210 and the rotary shaft 221 are rotated.

A process of driving the paper feeder 1 according to an embodiment of the present disclosure is described.

Referring to FIG. 3, a feed cassette 310 is in a state where it secedes from the image forming apparatus, and the paper feeder 1 is in a standby state in which the paper feeder 1 is unable to perform feeding. The first portion 210 of the support 200 is in a first position P1 in which the support 200 supports the pickup unit 100 so that the pickup unit 100 is maintained in a standby state, and thus the first surface 211 of the first portion 210 may come in contact with the supported portion 143 of the pickup unit 100.

As illustrated in FIG. 4, the feed cassette 310 including paper 311 is mounted. Since the feed cassette 310 is mounted, a pressing surface 312 of the feed cassette 310 presses the first portion 210 of the support 200. Accordingly, the first portion 210 and the rotary shaft 221 may be rotated about the fixed shaft 222 as the rotating shaft.

As the support 200 is rotated, the first portion 210 may be rotated to slide on the lower surface of the supported portion 143 from the first surface 211 to the second surface 212. The first portion 210 secedes from the supported portion 143. Accordingly, the pickup unit 100 is rotated in a direction A, in which the pickup roller 120 descends about the driving shaft 110 as a rotating shaft, for example, by self-weight. This rotation may be performed until the pickup roller 120 is seated on the paper 311. The support 200 is in a second position P2 that is pushed by the feed cassette 310.

If the paper 311, for example, is entirely consumed, the feed cassette 310 may be separated from the image forming apparatus to provide the feed cassette 310 with paper 311. Since the rotary shaft 221 and the fixed shaft 222 may be coupled to each other by the elastic member, the support 200 returns to the first position P1 as the feed cassette 310 secedes from the image forming apparatus. The first portion 210 lifts the pickup unit 100 as the second surface 212 starts to come in contact with the supported portion 143, and slides on the lower surface of the supported portion 143 to return to the first position P1.

This process can be performed since the force by which the support 200 returns from the second position P2 to the first position P1 may be higher than the force by which the pickup unit 100 is rotated due to the self-weight.

Referring to FIG. 5, the paper feeder 1 according to an exemplary embodiment of the present disclosure may include a pressing member that can apply an additional rotating force to press the paper in a direction B together with the self-weight of the pickup unit 100.

The pressing member may be a torsion spring 161 having one end 162 that is fixed to the housing 140 and the other end 163 that is fixed to a washer 111 that is fitted to slip on the driving shaft 110.

If the pickup roller 120 does not come in contact with the paper, the washer 111 and the torsion spring 161 may be rotated together with the driving shaft 110, while if the pickup roller 120 comes in contact with the paper, the washer 111 and the torsion spring 161 slip without being rotated together with the driving shaft 110.

The washer 111 may continuously apply a rotating force in the rotating direction of the driving shaft 110 by a frictional force between the driving shaft 110 and the washer 111, and thus the torsion spring 161 may apply a rotating force to rotate the pickup unit 100 in the direction B.

Referring to FIG. 6, the pressing member that applies an additional rotating force together with the self-weight of the pickup unit 100 as illustrated in FIG. 5 may be a coil spring 171 that may be positioned, for example, on an upper side of the pickup unit 100.

The coil spring may have one end 172 that is fixed to the housing 140 and the other end 173 that is fixed to a structure 174 that may be fixedly arranged on the upper portion of the pickup unit 100.

The coil spring 171 is in a compression state and applies force to push the pickup unit 100 from the structure 174. This force makes the pickup unit 100 be rotated, for example, in a direction C in which the pickup roller 120 descends about the driving shaft 110.

In the case where the pickup unit 100 is in a feeding state, the pressing member increases the frictional force between the pickup roller 120 and the paper 311 to reduce a slip between the pickup roller 120 and the paper 311.

Referring to FIGS. 7 to 9, a paper feeder 1 a according to an exemplary second embodiment of the present disclosure is described. In describing the configuration of the second embodiment, the same drawing reference numerals are used for the same elements as those according to an exemplary first embodiment as described above. The description of the same elements is omitted.

Referring to FIG. 7, a guide projection 144 having a predetermined length may be formed to project from a side surface of the housing 140 of the pickup unit 200.

A support roller 213 to support the pickup unit 100 may be rotatably installed on the first portion 210 of the support 200 to come in contact with the guide projection 144.

A process of driving the paper feeder 1 a according to the second embodiment of the present disclosure is described.

Referring to FIG. 8, the feed cassette 310 is in a state where it secedes from the image forming apparatus, and the paper feeder 1 a is in a standby state in which the paper feeder 1 a is unable to perform feeding.

The first portion 210 of the support 200 is in a first position P1 in which the support 200 supports the pickup unit 100 so that the pickup unit 100 is maintained in a standby state, and thus the support roller 213 of the first portion 210 comes in contact with the guide projection 144 of the pickup unit 100.

Referring to FIG. 9, the feed cassette 310 that is filled with the paper 311 is mounted. Since the feed cassette 310 is mounted, the pressing surface 312 of the feed cassette 310 presses the first portion 210 of the support 200. Accordingly, the first portion 210 and the rotary shaft 221 are rotated about the fixed shaft 222 as the rotating shaft.

As the support 200 is rotated, the support roller 213 is rotated along the surface of the guide projection 144, and finally secedes from the guide projection 144. Accordingly, the pickup unit 100 is rotated in an arrow direction A, in which the pickup roller 120 descends about the driving shaft 110 as a rotating shaft, by self-weight. This rotation is performed until the pickup roller 120 is seated on the paper 311.

The support 200 is in the second position P2 that is pushed by the feed cassette 310. The length of the first portion 210 and the position of the guide projection 144 may be adjusted in order to prevent the driving shaft 110 from interfering with the rotating path of the support roller 213.

If the paper 311 is consumed, the feed cassette 310 may be made to secede from the image forming apparatus to allow refilling of the feed cassette 310 with the paper 311.

Since the feed cassette 310 secedes from the image forming apparatus, the support is rotated in a reverse direction to the arrow direction A to return to the first position P1. The support roller 213 starts to come in contact with one surface of the guide projection 144 to lift the pickup unit 100, and may rotate along the surface of the guide projection 144 to return to the first position P1.

This process can be performed since the force by which the support 200 returns from the second position P2 to the first position P1 may be greater than the force by which the pickup unit 100 is rotated due to the self-weight.

The paper feeder 1 a according to a second embodiment of the present disclosure may include a pressing member as illustrated in FIGS. 5 and 6 to reduce a slip between the pickup roller 120 and the paper 311 through increasing of the frictional force between the pickup roller 120 and the paper 311 when the pickup unit 100 is in a feeding state.

Referring to FIGS. 10 to 12, a paper feeder 1 b according to a third embodiment of the present disclosure is described. In describing the configuration of the third embodiment, the same drawing reference numerals are used for the same constituent elements as those according to the first embodiment as described above. According to the third embodiment of the present disclosure, the paper feeder 1 b is applied to the image forming apparatus on which a feed tray 320 is mounted.

Referring to FIG. 10, the feed tray 320 may always be mounted on the image forming apparatus, and the paper feeder 1 b is in a standby state in which the paper feeder 1 b is unable to perform feeding. The first portion 210 of the support 200 is in a first position L1 in which the support 200 supports the pickup unit 100 so that the pickup unit 100 is maintained in a standby state, and thus the first surface 211 of the first portion 210 comes in contact with the supported portion 143 of the pickup unit 100.

Referring to FIG. 11, the paper 321 is set in the feed tray 320. Since the paper 321 is set, the front end 322 of the paper 321 presses the first portion 210 of the support 200. Accordingly, the first portion 210 and the rotary shaft 221 are rotated about the fixed shaft 222 as the rotating shaft.

As the support 200 is rotated, the first portion 210 is rotated along the lower surface of the supported portion 143 from the first surface 211 to the second surface 212, and finally, the first portion 210 secedes from the supported portion 143. Accordingly, the pickup unit 100 is rotated in a direction D, in which the pickup roller 120 descends about the driving shaft 110 as a rotating shaft, by the self-weight. This rotation is performed until the pickup roller 120 is seated on the paper 321. The support 200 is in a second position L2 that is pushed by the paper 321.

However, the second position L2 in the case where the paper feeder 1 b according to the present disclosure is applied to the type in which the paper 321 is inserted into the feed tray 320 is different from the second position P2 in the type in which the feed cassette 310 is mounted, and the support 200 is rotated to the extent that the second position L2 is pushed by the paper 321. Accordingly, in the process of feeding the paper 321 into the image forming apparatus through the feed roller 150, the paper 321 pushes the support 200 up to a third position L3.

Referring to FIG. 12, the third position L3 is illustrated, and the paper 321 naturally pushes the support 200 and is fed into the image forming apparatus by the feed roller 150.

If the paper 321 that presses the support 200 is entirely consumed, in a similar manner as the above-described embodiments, the support 200 returns to the first position L1, for example, by the elastic member that makes the rotary shaft 221 and the fixed shaft 222 coupled to each other. The first portion 210 of the support 200 lifts the pickup unit 100 as the second surface 212 starts to come in contact with the supported portion 143, and slides on the lower surface of the supported portion 143 to return to the first position L1.

This process can be performed since the force by which the support 200 returns from the second position L2 to the first position L1 is greater than the force by which the pickup unit 100 is rotated due to the self-weight. Since the force by which the paper 321 presses the support 200 is greater than the force by which the support 200 returns from the second position L2 to the first position L1, the paper 321 can push the support 200.

The paper feeder 1 b according to the third embodiment of the present disclosure may also include a pressing member as illustrated in FIGS. 5 and 6 to reduce a slip between the pickup roller 120 and the paper 321 through increasing of the frictional force between the pickup roller 120 and the paper 321 when the pickup unit 100 is in a feeding state.

Referring to FIGS. 13 to 15, a paper feeder 1 c according to a fourth embodiment of the present disclosure is described. In describing the configuration of the fourth embodiment, the same drawing reference numerals are used for the same elements as those according to the second embodiment as described above. According to the fourth embodiment of the present disclosure, the paper feeder 1 c is applied to the image forming apparatus on which a feed tray 320 is mounted.

Referring to FIG. 13, the feed tray 320 may be always mounted on the image forming apparatus, and the paper feeder 1 c is in a standby state in which the paper feeder 1 c is unable to perform feeding. The first portion 210 of the support 200 is in a first position L1 in which the support 200 supports the pickup unit 100 so that the pickup unit 100 is maintained in a standby state, and thus the support roller 213 of the first portion 210 comes in contact with the guide projection 144 of the pickup unit 100.

Referring to FIG. 14, the paper 321 is set in the feed tray 320. Since the paper 321 is set, the front end 322 of the paper 321 presses the first portion 210 of the support 200. Accordingly, the first portion 210 and the rotary shaft 221 are rotated about the fixed shaft 222 as the rotating shaft.

As the support 200 is rotated, the support roller 213 is rotated along the surface of the guide projection 144, and finally secedes from the guide projection 144. Accordingly, the pickup unit 100 is rotated in a direction D, in which the pickup roller 120 descends about the driving shaft 110 as a rotating shaft, by the self-weight. This rotation is performed until the pickup roller 120 is seated on the paper 321. The support 200 is in a second position L2 that is pushed by the feed cassette 310.

However, the second position L2 in the case where the paper feeder 1 c according to the present disclosure is applied to the type in which the paper 321 is inserted into the feed tray 320 is different from the second position P2 in the type in which the feed cassette 310 is mounted, and the support 200 is rotated to the extent that the second position L2 is pushed by the paper 321. Accordingly, in the process of feeding the paper 321 into the image forming apparatus through the feed roller 150, the paper 321 pushes the support 200 up to a third position L3. The length of the first portion 210 and the position of the guide projection 144 may be adjusted in order to prevent the driving shaft 110 from interfering with the rotating path of the support roller 213.

Referring to FIG. 15, the third position L3 is illustrated, and unlike the first portion 210 according to the third embodiment, the support roller 213 is provided on the first portion 210 according to the fourth embodiment. Accordingly, the paper 321 naturally pushes the support 200 and is fed into the image forming apparatus by the feed roller 150.

If the paper 321 that presses the support 200 is entirely consumed, in the same manner as the above-described embodiments, the support 200 returns to the first position L1 by the elastic member that makes the rotary shaft 221 and the fixed shaft 222 coupled to each other. The support roller 213 starts to come in contact with one surface of the guide projection 144 to lift the pickup unit 100, and is rotated along the surface of the guide projection 144 to return to the first position L1.

This process can be performed since the force by which the support 200 returns from the second position L2 to the first position L1 is greater than the force by which the pickup unit 100 is rotated due to the self-weight. Since the force by which the paper 321 presses the support 200 is higher than the force by which the support 200 returns from the second position L2 to the first position L1, the paper 321 can push the support 200.

The paper feeder 1 c according to the fourth embodiment of the present disclosure may also include a pressing member as illustrated in FIGS. 5 and 6 in order to reduce a slip between the pickup roller 120 and the paper 321 through increasing of the frictional force between the pickup roller 120 and the paper 321 when the pickup unit 100 is in a feeding state.

As described above, according to the present disclosure, in a case where paper 311 or 321 is loaded, the pickup roller 120 always comes in contact with the paper 311 or 321, and thus impact noise that is generated between the pickup roller 120 and the paper 311 or 321 during the feeding operation can be eliminated.

While the present disclosure has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present disclosure, as defined by the appended claims.

Although a few embodiments have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents. 

What is claimed is:
 1. A printing medium feeder comprising: a pickup unit configured to pick up a printing medium; and a support arranged on a lower side of the pickup unit to selectively support the pickup unit or release supporting of the pickup unit, wherein as the support releases the supporting of the pickup unit, an other end portion of the pickup unit descends by a self-weight on a basis of one end portion thereof to be seated on the printing medium.
 2. The printing medium feeder of claim 1, wherein the support swings about a lower end portion thereof to support a part of a lower side of the pickup unit through an upper end portion thereof.
 3. The printing medium feeder of claim 2, wherein the support is pressed by a feed cassette mounted on a main body or the printing medium set on a feed tray and swings in a mounting direction of the feed cassette or in a printing medium setting direction to release the supporting of the pickup unit.
 4. The printing medium feeder of claim 3, wherein the support comprises an elastic member provided in the lower end portion thereof, and returns to its original position by the elastic member to support the pickup unit if the feed cassette secedes from its mounted position or the printing medium set on the feed tray is entirely consumed.
 5. The printing medium feeder of claim 2, wherein the support comprises a support roller provided on the upper end portion thereof to come in contact with and to slide along the part of the lower side of the pickup unit.
 6. The printing medium feeder of claim 1, wherein the pickup unit includes a guide projection formed to project from the lower side thereof in a side direction, and the support includes a support roller configured to support the guide projection.
 7. The printing medium feeder of claim 1, wherein the pickup unit further comprises a pressing member configured to elastically press the other end portion of the pickup unit so that a pickup roller arranged on the other end portion of the pickup unit presses the printing medium.
 8. The printing medium feeder of claim 7, wherein the pressing member is a torsion spring provided on a driving shaft that penetrates the one end portion of the pickup unit.
 9. The printing medium feeder of claim 7, wherein the pressing member that presses the other end portion of the pickup unit in a lower direction is a coil spring that presses from an upper portion of the pickup unit toward the lower side.
 10. The printing medium feeder of claim 9, wherein the coil spring has one end that is fixed to a part of a structure that is positioned on an upper side of the pickup unit and the other end that is fixed to an upper side of the other end portion of the pickup unit, and elastically presses the pickup unit.
 11. A printing medium feeder comprising: a pickup unit configured to pick up a printing medium; and a support arranged on a lower side of the pickup unit, wherein the support is selectively set to a first position in which the support supports the pickup unit or a second position in which the support is pressed by a feed cassette that is mounted on a main body or the printing medium that is set on a feed tray of an image forming apparatus to release the supporting of the pickup unit.
 12. The printing medium feeder of claim 11, wherein the pickup unit is rotated so that an other end portion thereof descends by self-weight on the basis of one end portion thereof to be seated on the printing medium as the support is rotated from the first position to the second position, and is rotated so that the other end portion thereof ascends on the basis of the one end portion thereof as the support is rotated from the second position to the first position.
 13. The printing medium feeder of claim 12, wherein the support comprises an elastic member provided in a lower end portion thereof to be elastically rotated from the second position to the first position.
 14. An image forming apparatus comprising: a main body; a feed cassette detachably provided on the main body or a feed tray provided on the main body on which to set a printing medium; and a printing medium feeder including a pickup unit configured to pick up the printing medium, and a support arranged on a lower side of the pickup unit to support the pickup unit in a first position and to release the supporting of the pickup unit in a second position, wherein an other end portion of the pickup unit swings downward from the second position by self-weight on the basis of one end portion thereof so that a pickup roller of the pickup unit is seated on the printing medium.
 15. The image forming apparatus of claim 14, wherein the support is rotated from the first position to the second position as the support is pressed by the feed cassette mounted on the main body or the printing medium that is set in the feed tray.
 16. The image forming apparatus of claim 15, wherein the support is rotated from the second position to the first position as the support is released from being pressed by the feed cassette or the printing medium of the feed tray. 